Apparatus for varying the engine torque in particular operating states of an internal combustion engine

Abstract: The system comprises sensors (3) which detect parameters of the engine; an electronic injection device (4) a block which controls the injection device in normal fuel-air mixture-delivery conditions; means (23) which compare for each engine phase the value (F) of the position of the air induction manifold butterfly valve with a first threshold value (MF1); means (24) which for each engine phase, compare the value (RPM) of the engine speed with a second threshold value (MRPM1); and means (25), activated if the value of the butterfly position is less than the first threshold value and the value of the engine speed is greater than the second threshold value to control, for each cylinder of the engine and according to a table (28) the rate of flow of fuel-air mixture so as to change from normal fuel-delivery conditions to a fuel mixture cut-off condition with a predetermined law of variation of engine torque.

Description: The present invention relates to an apparatus controlling the engine torque of a vehicle. In particular, the apparatus forming the subject of the present invention relates to a control strategy for controlling the introduction of fuel into the cylinders of the engine, causing it to change from a normal fuel-delivery condition to a fuel cut-off condition and vice versa. As is known, in motor vehicles it is desirable to cut off the fuel delivery when useful power from the engine is not required, that is to say when the accelerator pedal is completely released (and therefore when the induction manifold butterfly valve reaches the minimum position) and when simultaneously the speed of the engine is greater than a predetermined threshold value. Normal fuel-delivery conditions are reintroduced (from the fuel cut-off condition) when the accelerator pedal is pressed (and therefore when the induction manifold butterfly valve is displaced from its minimum position) or when the speed of rotation of the engine is less than the predetermined threshold value. Systems currently in use which allow the change from normal fuel-delivery conditions to fuel cut-off conditions and vice versa envisage, in equal measure for all cylinders of the engine and after a predetermined time or after a predetermined number of engine phases, the cut-off (or increase) by 100% of the fuel in one or two stages. According to what is described in French Patent Application N° 2406080, it is known to progressively modify, during the entry in a cut-off condition, the fuel supply to the cylinders of an internal combustion engine in order to smooth transients in engine output torque. GB-A-2 138 176 proposes-during fuel recovery-after a cut-off condition, the use of several fuel increment tables, the tables being selected according the magnitude of change of the engine speed. The systems just described involve several disadvantages which exhibit themselves in particular in making the vehicle unpleasant to drive due to the sharp change from positive torque conditions to negative torque conditions and vice versa; which sharp transfer causes jerks and jolts of the engine. It is clear that the vibration which thus occurs in the engine increases the wear of the various parts of the engine. Moreover, in passing from fuel cut-off conditions to normal delivery conditions the quantity of fuel to provide is defined, in a single solution, independently from the reason (variation in the induction butterfly angle or variation in the speed of rotation of the engine) which causes the return to normal fuel-delivery conditions. It can be understood therefore, that, if the reason is a request for higher power from the engine the engine response is less than expected. The object of the present invention is that of providing a system for varying the drive torque in particular operating conditions of a heat engine of a motor vehicle, which will be free from the above mentioned disadvantages and which, therefore, reduces the engine vibrations upon change from a normal fuel-delivery condition to a fuel cut-off condition and vice versa. This object is achieved with the features according to claim 1. For a better understanding of the present invention a preferred embodiment will now be described purely by way of non limitative example, with reference to the attached drawings, in which: Figure 1 is a block diagram of a system formed according to the principles of the present invention; Figures 2 and 3 are operating diagrams of the system of figure 1; Figure 4 is a flow diagram of one of the units of the operating diagrams of figures 2 and 3; and Figure 5 is a table of coefficients. As illustrated in figure 1, a system for varying the drive torque of a heat engine (not illustrated) of a vehicle (not illustrated) in particular conditions is generally indicated with the reference number 1. In particular the system 1 controls the induction of the air-fuel mixture to the cylinders (not illustrated) of the engine to change from a normal delivery condition of the fuel-air mixture to a mixture cut-off condition and vice versa. The system 1 comprises: an electronic central control unit 2; a plurality of sensors 3 connected to the central control unit 2 and operable to detect parameters of the engine such as the engine's speed of rotation, the engine phase, the angular position of the butterfly (throttle) valve (not illustrated) of the air induction manifold (not illustrated), the engine coolant fluid temperature, the inducted air temperature, the battery voltage of the battery (not illustrated) of the vehicle, and others; an electronic fuel injection device 4 controlled by the central control unit 2; an electronic ignition device 5 controlled by the central control unit 2; a device 6 for controlling a fuel pump (not illustrated), which device is managed by the central control unit 2; a device 7 for management of the rate of flow of aspirated air from the induction manifold; and a device 8 mounted on the dashboard (not illustrated) of the vehicle and operable to indicate the cut-off condition and the conditions of entering and leaving the cut-off condition. With reference to figure 1, the central control unit 2 comprises; a unit 9 for detecting the magnitudes of the input signals from the sensors 3; a memory block 11 in which is stored, for each operating range of the engine, the management mappings for the devices 4,5,6 and 7; a memory block 12 in which are stored threshold values and the values of the coefficients which will be described hereinafter; a control block 13 for the devices 4,5,6 and 7 in normal fuel-air mixture delivery conditions; a block 14 for control of the devices 4,5,6,7 and 8 during the transfer from a normal fuel-air mixture delivery condition to a mixture cut-off condition and vice versa; a data processing and comparison block 15 for management of the blocks 13 and 14; and a counter 16 connected to the block 15. In use, in dependence on the value of the quantities detected by the sensors 3 the block 15 calculates the engines operating region, takes from the calculated range block 11 the management maps for the devices 4,5,6 and 7, and controls the block 13 according to the data of these maps, which then controls the devices 4,5,6 and 7. With reference to figure 2, an operating cycle of the system 1 will now be described, which permits the transfer from a normal mixture delivery condition represented by a block 21 to a mixture cut-off condition represented by a block 22. Each engine phase, that is to say each 180° of the engine crankshaft, the system passes from block 21 to a block 23 in which the detected value F of the angular position of the induction manifold butterfly valve is compared with a threshold value MF1 memorised in block 12. If the value F is less than or equal to the value MF1, the system passes from block 23 to a block 24, whilst if not it returns from block 23 to block 21. In block 24 the detected value RPM of the speed of rotation of the engine is compared with a threshold value MRPM1 memorised in block 12. If the value RPM is greater than or equal to the value MRPM1, the system passes from block 24 to a block 25, whilst otherwise it returns from block 24 to block 21. In block 25 the unit 14 performs a control strategy on devices 4,5,6,7 and 8 for the purpose of changing to the cut-off condition in a predetermined number of engine phases N (which condition does not permit any flow of mixture to the engine) and for the purpose of indicating to the user the change to this cut-off condition by means of the device 8. Once the strategy of variation of the flow of mixture is defined and put into effect the system passes from block 25 to a block 26 in which, in unit 15 the value F is compared with the threshold value MF1. If the value F is less than or equal to the value MF1 the system passes from block 26 to a block 27, whilst otherwise it returns from block 26 to block 21. In block 27 the value RPM is compared with the threshold value MRPM1. If the value RPM is greater than or equal to the value of MRPM1 the system passes from block 27 to block 22, whilst otherwise it returns from block 27 to block 21. In Figure 4 is illustrated a preferred embodiment of the strategy performed by the block 25. In this strategy a table 28 (Figure 5) of coefficients Ki memorised in block 12 is utilised. The table 28 comprises N cells to each of which is associated a value of the coefficient Ki. The block 25 includes a block 31 in which a quantity C is made to assume the value 1 in the counter 16; the quantity C being related to the sequence of cells of the table 28. From block 31 the system passes to a block 32 in which the operating condition of the engine is evaluated and the injection time Tj for this operating condition is calculated. From block 32 the system passes to a block 33 in which it takes the coefficient Ki1 from the first cell, being C=1, of the table 28. From block 33 the system passes to a block 34 in which the injection time Tj just calculated is multiplied by the coefficient Ki1 in such a way as to define a new injection time Tji1. In block 34 the cylinder in the induction phase is controlled to have a fuel mixture injection according to the new injection time Tji1. From block 34 the system passes to a block 35 in which it is determined if the quantity C is greater than the number N of cells in the table 28. If this is so it passes from block 35 to a block 37 and from this to block 26 of Figure 2, whilst otherwise it passes from block 35 to a block 36 in which the quantity C of the counter 16 is incremented by one unit. From block 36 the system then returns to the block 32. In block 37 the device 8 is activated to indicate, for example by means of a warning lamp (not illustrated) the change to mixture cut-off conditions. The block 25 allows the injection time Tji1 to be calculated cylinder by cylinder following a variation of the engine operating conditions. The values of the coefficients Ki are processed in such a way as to vary the engine torque during the change from normal mixture-delivery conditions to cut-off conditions according to a law which does not involve sharp changes and therefore engine shocks. Other parameters can contribute to the processing of the law of variation of the engine torque in different embodiments, such as the variation of the electronic ignition advance (by suitably managing the device 5), the variation in control of the fuel pump (by suitably managing the device 6) and/or the variation of the rate of flow of inducted air (by suitably managing the device 7). In essence, as well as the flow of mixture cylinder by cylinder, it is possible to vary the combustion times, the total flow of fuel, and the stoichiometric ratio of the mixture. With reference to figure 3, an operating cycle of the system 1 will now be described which permits the change from mixture cut-off conditions represented by the block 22, back to normal delivery conditions represented by the block 21. Each engine phase, that is each 180° of the engine crankshaft, the system passes from block 22 to a block 41 in which, in unit 15 the value Qa detected by a sensor 3, and relating to the rate of flow of air along the induction manifold, is compared with a threshold value MQa memorised in unit 12. If Qa is greater than MQa the system passes from block 41 to a block 42, whilst otherwise it passes from block 41 to a block 43. In block 43 the detected value F of the angular position of the induction manifold butterfly valve is compared with a minimum threshold value MF2 memorised in unit 12. If the value F is less than or equal to the value MF2 the system passes from block 43 to a block 44 whilst otherwise it passes from block 43 to block 45. In block 44 the detected value RPM of the speed of rotation of the engine is compared with a threshold value MRPM2 memorised in unit 12. If the value RPM is greater than or equal to the value MRPM2 the system returns from block 44 to block 22 whilst otherwise it passes to a block 46. In block 45 the system compares the angular variation of the induction manifold butterfly valve, in a predetermined time δF/δt with the threshold value MFt memorised in unit 12. If the value δF/δt is greater than or equal to the value MFt the system passes from block 45 to a block 47, whilst otherwise it passes from block 45 to block 48. In block 46 the system compares the variation of the speed of rotation of the engine in a predetermined time δRPM/δt with a threshold value MRPMt memorised in unit 12. If the value δRPM/δt is greater than or equal to the value MRPMt, the system passes from block 46 to a block 51, whilst otherwise it passes from block 46 to block 52. In block 41, in place of the rate of flow of inducted air a different quantity representative of the behaviour of the inducted air can be utilised, for example the parameter relating to the inducted air pressure can be utilised. In any event, the parameter utilised in unit 41 detects possible rapid and unwanted decreases in the speed of rotation of the engine. In block 43 the angular position of the air induction manifold butterfly valve and therefore the angular position of the accelerator pedal is evaluated, which position represents the user's wish to leave the cut-off condition. In block 45 the rate of change of the angular position of the butterfly valve is evaluated and essentially gives the pressure exerted by the user on the accelerator pedal. In block 44 the value of the speed of rotation of the engine is evaluated and in block 46 the rate of change of the engine speed is evaluated. The system 1 envisages exit from the cut-off condition upon a variation in the rate of flow of inducted air (block 41), a variation in the angular position of the butterfly valve (block 43), and a variation in the engine speed (block 44). Moreover, the system 1 detects the way in which the angular position of the butterfly valve varies (block 45) and the way in which the speed of rotation of the engine (block 46) varies. Essentially the system 1 envisages five possibilities (blocks 42,47,48,51 and 52) to determine the exit from the cut-off condition. In block 12 five tables similar to the table 28 are memorised, each of which relates to a condition for exit from the cut-off condition. In blocks 42,47,48,51 and 52 the associated table is therefore taken from block 12. From blocks 42,47,48,51 and 52 the system passes to a block 53 similar to block 25 of Figures 2 and 4, and from block 53 it moves on to block 21 which represents the normal fuel mixture delivery conditions. The operating diagram of block 25 illustrated in Figure 4 can be assumed as an operative scheme also for block 53. In fact, a command strategy is performed in block 53, by means of the block 14, for control of devices 4,5,6,7 and 8 for the purpose of changing, in a predetermined number of engine phases N, from the mixture cut-off condition to normal mixture-delivery conditions, and for the purpose of indicating to the user, by means of the device 8, this change to normal mixture-delivery conditions. In Figure 4, alongside the reference numerals for the components of the block 25, and in parenthesis, are indicated the components of the block 53. In the strategy carried out by block 53 is utilised a table (corresponding to blocks 52,47,48,51 or 52 via which the block 53 is reached) of coefficients Ko memorised in block 12. The table comprises N cells to each of which is associated a value of the coefficient Ko. The block 53 includes a block 54 in which a quantity D is caused to assume the value 1 in counter 16; quantity D being associated with the sequence of cells of the said table. From block 54 the system passes to a block 55 in which the engine operating condition is evaluated and the injection time Tj is calculated for that operating condition. From block 55 the system passes to a block 56 in which it takes the co-efficient Ko1 from the first cell, being D=1, of the table the coefficient K01. From block 56 the system passes to a block 57 in which the injection time Tj just calculated is multiplied by the coefficient Ko1 in such a way as to define a new injection time Tjo1. In block 57 it further controls, for each cylinder in the induction phase, a mixture injection according to the new injection time Tjo1. From block 57 the system passes to a block 58 in which it evaluates if the quantity D is greater than the number N of cells in the said table. In the positive case it passes from block 58 to a block 62 and from this to block 21 of Figure 3, whilst otherwise it goes from block 58 to a block 61 in which it increments by one unit the value of the quantity D of the counter 16. From block 61 it then returns to block 55. In block 62 it activates the device 8 which indicates, by means of a warning lamp (not illustrated), the change to normal mixture delivery conditions. Therefore, as a function of the type of exit condition from the cut-off state, and cylinder by cylinder, the block 53 calculates an injection time Tjo1 following the variations in the operating conditions of the engine. The values of the coefficients Ko are processed in such a way as to vary the engine torque, during the change from mixture cut-off conditions to normal delivery conditions, in dependence on a law of variation which does not involve sharp changes and therefore jolts or jerks of the engine. In block 53 the processing of the law of variation of the engine torque can also be in different forms, and can involve other parameters such as the variation of the electronic ignition advance, the variation of the fuel pump control, and/or variation of the rate of flow of inducted air. From what has been described the advantages achieved with the embodiments of the present invention are apparent. In particular, there is formed a system which makes it possible to graduate the variations in the engine torque in such a way as to avoid sharp jerks of the engine both when entering and when leaving the fuel cut-off condition. The manner in which the flow of air-fuel mixture is controlled contributes in a particular way to the law of variation of the engine torque; the manner processed for each cylinder is updated for each engine phase to follow the engine operating conditions. In changing from the cut-off condition to normal delivery conditions it is possible to choose a law of variation of engine torque in dependence on the variation of the values of several parameters and the rate of variation of these values. In this way the wishes of the user can be followed with greater promptness. Finally, it is clear that the system 1 described and illustrated here can have modifications and variations introduced thereto without. In particular, the laws of variation of the engine torque both when entering and leaving the cut-off condition, and in substance the tables of coefficients Ki and Ko can be the most varied possible. It is therefore possible to adapt the laws of variation of the engine torque upon entering and leaving the fuel cut-off condition both to the type of engine installed on the vehicle and to the performance which it is wished to obtain from the engine, particularly when leaving the fuel cut-off condition.

Claims: Apparatus controlling the engine torque of a vehicle, comprising: a plurality of sensors (3) operable to detect the parameters of the engine such as the speed of rotation, the engine phase, the angular position of the air induction manifold butterfly valve, the temperature of the engine coolant fluid, the temperature of the inducted air, the battery voltage and others; an electronic fuel injection device (4); a memory block (11) in which are memorised, for each operating condition of the engine, management maps for the said fuel injection device (4); a block (13) for controlling said injection device (4) in normal fuel/air mixture-delivery conditions; a block (15) for processing and comparing data, operable to process the parameters of the engine and to manage the said control block (13); first comparison means (23) for comparing, for each engine phase, the detected value (F) of the angular position of the air induction manifold butterfly valve with a first threshold value (MF1); second comparison means (24) for comparing, for each engine phase, the detected value (RPM) of the speed of rotation of the engine with a second threshold value (MRPM1); first control means (25), activated when the said value (F) of the angular position of the butterfly valve is less than the said first threshold value (MF1) and the said value (RPM) of the speed of rotation of the engine is greater than the said second threshold value (MRPM1), to control, for each cylinder of the engine and according to a predetermined first table (28), the flow of mixture to pass, in a predetermined time period, from the normal fuel mixture delivery condition to a mixture cut-off condition with a predetermined law of variation of engine torque; the apparatus being characterised in that it comprises means for detecting the rate of variation (δF/δt and δRPM/δt) of the detected value (F) of the angular position of the induction manifold butterfly valve and the detected value (RPM) of the engine speed, and it also includes five second tables, the first relating to a variation greater than a determined third threshold value (MFt) of the said value (F) of the angular position of the butterfly valve, the second relating to a variation lower than the said third threshold value (MFt) of the said value (F) of the angular position of the said butterfly valve, the third relating to a variation greater than a determined fourth threshold value (MRPMt) of the said value (RPM) of the engine speed, the fourth relating to a variation greater than the said fourth threshold value (MRPMt) of the said value (RPM) of the engine speed, and the fifth relating to a variation beyond a fifth threshold value (MQa) of a value (Qa) corresponding to a parameter of the air inducted along the said induction manifold. Apparatus according to claim 1, characterised in that the said first table (28) comprises, in a determined sequence, a plurality of first coefficients (Ki) each of predetermined value, the said first coefficients (Ki) being associated with the number of engine phases set for passage from the normal mixture-delivery condition to the mixture cut-off condition; said first control means (25) including a block (32) which determines, for each engine phase, and according to the engine parameters, the engine operating conditions and from this the injection time (Tj) relating to the cylinder in its induction stroke during that engine phase, and a block (34) which calculates for each engine phase a new injection time (Tji1) as a function of the injection time (Tj) calculated on the basis of the engine operating conditions and one of the said first coefficients (Ki), and which further controls, for each cylinder in its induction stroke, an injection of mixture according to the new injection time (Tji). Apparatus according to claims 1 and/or 2, characterised in that it includes third comparison means (43), activated in fuel cut-off conditions, for comparing, for each engine phase, the detected values (F) of the angular position of the air induction manifold butterfly valve with a sixth threshold value (MF2); fourth comparison means (44), activated in fuel cut-off conditions, for comparing, for each engine phase, the detected value (RPM) of the speed of rotation of the engine with a seventh threshold value (MRPM2); second control means (53), activated when the said value (F) of the angular position of the butterfly valve is greater than the said sixth threshold value (MF2) or when the said value (RPM) of the engine speed is less than the said seventh threshold value (MRPM2), to control, for each engine cylinder and according to one of said five second tables, the flow rate of mixture so as to change, in a predetermined time period, from the mixture cut-off condition to the normal fuel-delivery condition with a predetermined law of variation of engine torque. Apparatus according to claim 3, characterised in that it includes fifth comparison means (41), activated in fuel cut-off conditions, for comparing, for each engine phase, the detected value (Qa) relating to the parameter of the air inducted along the said induction manifold, with the said fifth threshold value (MQa) to select said fifth second table as the proper second table; said second control means (53) being activated when the said value (Qa) relating to the parameter of the air inducted along the said induction manifold is greater than the said fifth threshold value (MQa). Apparatus according to claim 3 and/or 4, characterised in that each of said five second tables comprises a plurality of second coefficients (Ko) in a determined sequence, each said second coefficient being of predetermined value, the said second coefficients (Ko) being associated with the number of engine strokes set for passing from the mixture cut-off condition to the normal fuel-delivery condition; the said second control means (53) including a block (55) which, for each engine stroke and on the basis of the engine parameters, processes the engine operating conditions and from this the injection time (Tj) relating to the cylinder in its induction stroke during that engine phase, and a block (57) which calculates a new injection time (Tj01) for each engine phase as a function of the injection time (Tj) calculated on the basis of the engine conditions and one of the said second coefficients (Ko), and which further controls, for the cylinder in its induction stroke, a fuel mixture injection according to the new injection time (Tj0). Apparatus according to at least one of the preceding claims, characterised in that it includes means varying during the change from normal mixture-delivery condition to fuel cut-off condition, the control of a fuel delivery pump (6). Apparatus according to at least one of the preceding claims, characterised in that it comprises means varying during the change from mixture cut-off condition to normal fuel-delivery condition, the control of a fuel delivery pump (6). Apparatus according to at least one of the preceding claims, characterised in that it includes means varying during the change from normal mixture-delivery condition to fuel cut-off condition, the control of an electronic ignition device (5) to modify the ignition advance. Apparatus according to at least one of the preceding claims, characterised in that it includes means varying during the change from mixture cut-off condition to normal fuel-delivery condition, the control of an electronic ignition device (5) to modify the ignition advance. Apparatus according to at least one of the preceding claims, characterised that it includes means (8) for indicating the fuel/air mixture cut-off condition to the user.

Inventors: RICCIARDELLI GIANCARLO, SCOLARI STEFANO, RICCIARDELLI, GIANCARLO, SCOLARI, STEFANO
Applicants: MAGNETI MARELLI SPA, MAGNETI MARELLI S.p.A.
Application year: 1994
Main classification: F02D41
IPC codes: F02D41